This invention relates generally to interferometric apparatus and analysis and, more particularly, to the use of such analysis in connection with the detection and exploration of buried objects and hydrocarbons. Interferometric apparatus is also used to estimate elastic properties of associated earth material.
Originally, one type of signal was used to image and analyze earth materials in the subsurface. Seismic, acoustic, electromagnetic, and other types of signals are used for reflection, echolocation, diffraction, and excitation within earth materials. Signals are generated by transducers or other types of sources. Signals generated include discrete or continuous. Discrete signals are a timed event from a source or sources, such as explosive, dynamite, air guns, falling or fired weights, or any general pulse type source that occurs instantaneously, or as a timed event. Continuous signals result from a time-extended source such as a sonic, electromagnetic or radar source. These signals commonly suffer the drawback of containing only a single broadband signal. Likewise, receiver signals contain a single broadband signal. Examples of receiver signals are velocity pickups or electromagnetic transducers used in onshore seismic surveying, hydrophones or piezoelectric transducers used in water covered areas, and antennae used in radar or other electromagnetic surveying. Commonly used arrays consist of one type of transducer or a plurality of the same type of transducer, all having one natural frequency, one natural phase, or a flat amplitude spectrum. Unfortunately, frequency division and isolation used in spectral decomposition and analysis of received signals, as described in U.S. Pat. Nos. 5,414,674 and 6,131,071, are limited. Such signals cannot measure phase velocity. This communication system of source and receiver is used to identify buried earth materials and structures. As described in U.S. Pat. No. 4,316,267, amplitude information collected and processed utilizes an illumination of amplitude with offset (AVO) as the target signature. Amplitude information is normally collected and imaged by generation of broadband signals utilizing receiving devices consisting of one type of transducer or a plurality of the same type of transducer all having one natural frequency or flat spectrum. The target signature or AVO is used to locate gaseous hydrocarbons. Unfortunately, many large and deeper hydrocarbons go undetected.
It is another common industry practice to display images of buried objects using calculated surfaces from observed and received signals from tri-axial sensors. Such sensors are inexact, tedious, and uneconomic to deploy or interconnect, and attempts to measure dispersion and anisotropic characteristics of earth materials have not been reliable.
It would therefore be advantageous to provide, in accordance with the present invention, an apparatus and method for extracting and calculating the general elastic properties of earth materials, surfaces, targets, and hydrocarbons using independently recorded frequency or phase signals. An example of a receiver operating at multiple natural frequencies or natural phases is described in U.S. Pat. No. 5,335,208.
The present invention relates to a method and apparatus for the detection and exploration of buried objects and hydrocarbons employing at least two separate signals combined to form interferometric analysis and imaging of non-optical waves. These imaging systems include seismic, sonar, and radar imaging systems. The technique of measuring and analyzing absorption and other elastic moduli are shown from a three-dimensional analysis of interferometric information. The technique of interferometric holography also uses the unique characteristic record of frequency, phase, and amplitude of more than one signal. This type of analysis facilitates the estimation of elastic properties of earth material.
It is known that holographic visualizations result from image processing of different views of an object or surface commonly projected in three-dimensional space. Different views of the object or surface are normally associated with a measurement of offset. The present invention employs signals of different frequency or different bands of frequencies in imaging processes to generate holographic visualization. Specifically, signals of different frequency or different bands of frequencies may be directly viewed, graphed or projected onto a computer or projection screen to create holographic visualization. Holographic visualizations can be created using information gathered from offset interference measurements to display unique views. Such signals may be used to focus generated energy toward a buried object.
It would be further advantageous to provide, in accordance with the present invention, a method of velocimetry, illumination, and imaging.
It would be further advantageous to provide, in accordance with the present invention, a method for determining an estimate of the elastic parameters or properties of rock as related to the amplitude and phase of interferometric measurements.
It would be further advantageous to provide, in accordance with the present invention, a method of broadband or multiple band illumination using velocity imaging to construct homographic and holographic images of earth materials and buried structures.
It would be further advantageous to provide, in accordance with the present invention, a method of frequency banding or isolation for use in velocity imaging by employing frequency isolation with multiple frequencies.
It would be further advantageous to provide, in accordance with the present invention, a method for detecting subsurface hydrocarbons through the use of phase imaging and interferometric analysis.
It would be further advantageous to provide, in accordance with the present invention, a method for imaging horizontal components or performing shear wave analysis using interferometric analysis.
It would be further advantageous to provide, in accordance with the present invention, a method for imaging near surface structures such as mines, fractures or porosity.
It would be further advantageous to provide, in accordance with the present invention, a method for imaging sound by utilizing homographic analysis.
It would be further advantageous to provide, in accordance with the present invention, a method for determining range and depth of targets using selected frequency and phase information.
It would be further advantageous to provide, in accordance with the present invention, a method for producing a holographic image.
It would be further advantageous to provide, in accordance with the present invention, a method of analysis for diagnosing spectral absorption.
It would be further advantageous to provide, in accordance with the present invention, a frequency or phase modulated source of energy in the radar spectrum to detect hidden or buried objects.